NTSB Safety Recommendation P-26-003

NTSB safety recommendation P-26-003.

TO ATMOS ENERGY CORPORATION: Develop and implement a program to locate and replace all mechanical couplings and mechanical joints located in expansive soils that are not resistant to pipe pullout with couplings and joints developed specifically for those conditions. The program should establish and make public the project milestones and timeline.

Priority: CLASS II

Overall Status: Open - Initial Response Received

Issued Date: 2026-03-26

Adopted Date: 2026-03-12

Synopsis: This report discusses the January 2024 natural gas-fueled explosions and fires at two separate homes in Jackson, Mississippi, which occurred 3 days apart, collectively resulting in one injury, one fatality, and three destroyed homes. Safety issues identified in this report include compression coupling leaks, insufficient leak management program, inadequate distribution integrity management program, ineffective public awareness program, and absence of natural gas detection alarms in buildings.

Probable Cause: The National Transportation Safety Board determines that the probable cause of the two explosions at two separate homes in Jackson, Mississippi, was the service-line pipes partially pulling out of the compression couplings, likely because of soil movement (shrinking and swelling), creating natural gas leaks that Atmos Energy Corporation identified and left unrepaired for at least 8 weeks, which enabled gas to migrate to the nearby homes and ignite. Contributing to Atmos Energy Corporation’s failure to prevent the accidents were the operator’s: (1) insufficient leak management program, which did not determine appropriate monitoring timelines for leaks in adverse-soil conditions; (2) ineffective public awareness program, which did not adequately educate the public or emergency response officials on how to respond to a suspected natural gas leak; and (3) inadequate integrity management program, which did not appropriately assess and address risk in its Mississippi Division pipeline system.

Ntsbnumber: PLD24FR003

Report Number: PIR-26-01

Addressee Name: ATMOS Energy Corporation

Addressee Status: Open - Initial Response Received

Addressee Organization Type: P-Private Industry

Communication Date: 2026-03-26

Communication Type: Transmittal Letter

Communication Contents: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters. We are providing the following information to urge Atmos Energy Corporation to act on the safety recommendation in this letter because we believe your organization can help reduce the risk of future accidents. For more information about the NTSB and our recommendation process, please see the attached one-page summary. This letter also includes information about our March 12, 2026, report, Atmos Energy Corporation Natural Gas-Fueled Home Explosions and Fires, Jackson, Mississippi, January 24, 2024, and January 27, 2024, NTSB/PIR-26-01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, we identified the following safety issues: • Compression coupling leaks that the natural gas distribution operator had identified and left unrepaired. • Insufficient leak management program, which did not determine appropriate monitoring timelines for leaks in adverse-soil conditions. • Ineffective public awareness program, which did not adequately educate the public or emergency response officials on how to respond to a suspected natural gas leak. • Inadequate distribution integrity management program, which did not appropriately assess and address risk in its pipeline system. • Absence of natural gas detection alarms in buildings, which left occupants vulnerable to the dangers of unrecognized gas leaks. Accordingly, the NTSB makes the following safety recommendations to Atmos Energy Corporation (additional information regarding this recommendation can be found in the noted section of the report): • Develop and implement a program to locate and replace all mechanical couplings and mechanical joints located in expansive soils that are not resistant to pipe pullout with couplings and joints developed specifically for those conditions. The program should establish and make public the project milestones and timeline. (P-26-3) (See section 2.2.) • Update your companywide leak management program procedures to require weekly monitoring of nonhazardous (grade 2 or grade 3) belowground leaks identified in locations with adverse-soil conditions (such as water-saturated soil, flooding, drought, frozen ground, or settlement). (P-26-4) (See section 2.3.) • After completing the action described in P-26-4, implement a training program to maintain employee and contractor proficiency on the updated procedures. (P-26-5) (See section 2.3.) • Develop and implement a program to provide more frequent training to emergency response officials in all the distribution areas that you serve, including training on how to respond to natural gas-leak calls, and monitor the program for effectiveness. (P-26-6) (See section 2.4.) • Require your technicians who identify but do not repair a belowground natural gas leak to immediately notify people near the unrepaired leak that (1) the hazard potential of a leak can change over time, and (2) they should evacuate and then call 9 1 1 and Atmos Energy Corporation every time they smell natural gas odorant. (P-26-7) (See section 2.4.) • Develop and implement a program to proactively identify and collect missing service-line information for all your operating divisions. The program should (1) identify one or more methods for gaining additional system data and (2) establish and make public the milestones and timeline for acquiring the unknown system data. (P-26-8) (See section 2.5.) • Transition from a relative-risk model to a probabilistic distribution integrity management risk model. (P-26-9) (See section 2.5.) • Develop and implement a program that makes natural gas alarms available to members of the public who reside in your distribution areas. (P-26-10) (See section 2.6.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days of the date of this letter, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (Safety Recommendation P-26-3 through -10). We encourage you to submit your response to ExecutiveSecretariat@ntsb.gov. If your reply, including attachments, exceeds 20 megabytes, please e mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response. All communications regarding safety recommendations are stored by the NTSB and viewable by the public. Please do not send privileged or confidential communications in response to this recommendation. Responses marked as confidential or privileged (or similar designations) will be considered nonresponsive. In the likely event that your organization uses auto generated and/or preformatted confidentiality statements on letterhead or outgoing e-mails, please include a statement in your letter indicating that the information can be publicly released. If you have concerns about this protocol, please contact us at ExecutiveSecretariat@ntsb.gov. From Pipeline Investigation Report PIR-26-01 “Atmos Energy Corporation Natural Gas Fueled Home Explosions and Fires Jackson, Mississippi January 24, 2024, and January 27, 2024” published on March 26, 2026: Compression Coupling Leaks After the accidents, Atmos conducted pressure testing at both accident locations and identified leaks on compression couplings. These couplings were seal only, meaning they were not designed to resist pipe pullout and hold the service-line pipe in place. NTSB pressure testing on both accident pipeline assemblies identified leaks on the compression couplings between the couplings and the rest of the service lines. Footnote: The NTSB Materials Laboratory could not pressure test the Bristol Boulevard accident main and service line because they separated during excavation. However, NTSB Materials Laboratory pressure testing of the service-tee assembly and service-line pipe indicated that the leak was on the connection between the compression coupling and the service-line pipe, meaning the leak was on the compression coupling. At both accident locations, leaks occurred on compression couplings that were part of the service lines to homes that were across the street. Footnote: At the Bristol Boulevard location, the accident compression coupling was on the service line to the home at 190 Bristol Boulevard. At the Shalimar Drive location, the accident compression coupling was on the service line to the home at 1147 Shalimar Drive. Thus, near the accident homes, natural gas leaked from compression couplings that were part of nearby service lines. Before the accidents, Atmos leak surveys identified leaks near the accident homes. Atmos technicians classified the leaks as grade 2 (near the Bristol Boulevard accident home) and grade 3 (near the Shalimar Drive accident home) based on natural gas migration patterns present at the time of the leak survey and Atmos leak classification criteria (such as percentages of any gas detected in the air). Footnote: (a) The term “Atmos technicians” describes both Atmos employees and Atmos contractors. (b) Atmos technicians documented these leak surveys with ske

Addressee Organization Type: P-Private Industry

Communication Date: 2026-06-24

Communication Type: Official Correspondence

Communication Contents: -From John McDill, Senior Vice President Utility Operations: Atmos Energy appreciates the thoughtful review reflected in the NTSB recommendations in connection with the January 2024 incident in Jackson, Mississippi. We share the underlying objective of enhancing safety across our operations and in the industry. Atmos Energy has carefully evaluated each recommendation through a risk-informed lens, informed by our safety management system—called ACTS (Atmos Energy Culture of Trust and Safety), which emphasizes the importance of continuous improvement applied over our complex distribution system spanning eight states. Atmos Energy remains committed to ongoing collaboration with the NTSB, as well as with our federal and state regulators, to advance safety, strengthen system integrity, and support effective regulatory oversight. Our responses demonstrate this commitment to advancing safety performance and are consistent with the intent of the recommendations. Atmos Energy supports the objective of reducing risks associated with legacy mechanical couplings, including those located in expansive soils. Atmos Energy’s distribution integrity management program prioritizes the reduction of these risks in multiple respects, including a pipe replacement prioritization model that takes into consideration legacy joining methods. We also engage with each of our state regulators periodically to review and audit this program. This response further details programs that we have implemented to prioritize the risk of legacy mechanical couplings lacking resistance to pullout that were typically used to join steel service lines. They are summarized below, then they are more fully described as follows: • Historical Records – Efforts to address historical incomplete records to enhance our efforts to identify legacy mechanical couplings. • Distribution Integrity Model – Enhancements to the way we address mechanical couplings in our distribution integrity management model. Our distribution integrity model then guides mitigative actions, which we have also enhanced. • Pipe Replacement – While we have had a program of replacing legacy mechanical couplings on steel pipe where they lack restraint to pullout since at least 2013, we have also enhanced our pipe replacement prioritization with a risk-informed model that takes into consideration legacy pipe materials and joining practices. • Leak Management – Our leak management program provides additional data that drives mitigative actions to address risks identified in our distribution integrity model, including the risk of legacy mechanical couplings lacking resistance to pullout. We have made significant enhancements to our leak monitoring and repair efforts. Going above and beyond requirements of federal safety regulations, including those under 49 CFR Part 192, Atmos Energy has made extensive strides to address the risks of mechanical couplings not resistant to pullout. Atmos Energy’s approach is consistent with the regulatory framework for its distribution integrity management program. We focus on reducing risk through targeted, risk-informed actions, including those specifically addressing legacy mechanical couplings lacking resistance to pullout. Historical Records It is well known across the industry that historical installation records of assets, including mechanical fittings, can be inconsistent or unavailable due to a lack of regulatory requirements before 1970 and/or record keeping practices of legacy distribution systems, including those that Atmos Energy subsequently acquired. As a result, specific historical information about the number of mechanical fittings and their precise location is not always available. Recognizing this reality, Atmos Energy has implemented a layered approach designed to address both known and potentially undocumented mechanical coupling populations while continuously improving system knowledge over time. To address this, Atmos Energy has undertaken significant efforts to collect and electronically scan all known and available historical installation records and enter that information into our geographical information system (GIS). Through these efforts, Atmos Energy has scanned millions of records to update GIS. In addition, Atmos Energy undertakes significant efforts to supplement and continuously update system records during ongoing system monitoring, replacement, and maintenance activities. We continue to update and grow the knowledge of our system, such that previously missing, unknown, or incorrect data is adjusted via our map data correction process to update the GIS system. Thus, we work to continuously capture and validate our data through construction, maintenance, pipeline replacement, and other activities. Each of these activities has been foundational to our ability to identify the presence of legacy materials in our system, including mechanical couplings lacking resistance to pullout. These activities further inform the additional enhancements, below. Distribution Integrity Model Atmos Energy has enhanced our Distribution Integrity Management (DIM) models to reflect missing original record data and supplemented records with system knowledge from subject matter experts (SMEs) about installation practices, and other system characteristics. Atmos Energy has also reviewed our Distribution Integrity Management model and implemented enhancements to address mechanical couplings, their performance, and their operating environment through threat and risk assessment. These enhancements include: • Updated existing data sources related to soil properties, land cover and development intensity, and the proximity and difficulty of evacuating buildings. • Enhanced the methodology to represent the potential risk of mechanical couplings in both the Natural Forces and Equipment Failure threat assessments. Specifically, these included: • “Presence of Mechanical Fitting - Prior Failure” uses leaks where a mechanical fitting was involved to inform whether assets in the larger grid area may be susceptible to additional failures. • “Presence of Mechanical Fitting – Subject Matter Experts (SME)” uses SME knowledge of areas where mechanical fittings may be present, but may or may not have experienced a failure, to inform whether assets in the larger grid area may be susceptible to additional failures. • “Prior Fitting Failure Count” applies graduated levels of risk to mains and services based on the proximity and quantities of prior failures that have been indicated as having a mechanical fitting involved. In addition, we implemented in our distribution integrity risk model factors to account for the lack of access to original records regarding service lines and other data through appropriate weighting of factors and is supplemented with local SME knowledge of construction practices and materials. As an example, for the "Pipe Age" factor, if the installation date is unknown: • The install year of steel pipe is assumed to be 1945, which is representative of older steel pipe in the system. Steel Pipe Age: Current Year (2026) – 1945 = 81 years. In practice this applies a near worst case value within the “Pipe Age” factor – 1.8 out of 2.0. • The install year of plastic pipe is assumed to be 1970, which is representative of older plastic pipe in the system. Plastic Pipe Age: Current Year (2026) – 1970 = 56 years. In practice this applies a moderately unfavorable value within the “Pipe Age” factor – 1.5 out of 2.0. The application of weighting factors in the risk model to address incomplete information interacts with other enhancements to the risk model that improve our system knowledge. The distribution integrity model guides our mitigative actions, which includes both pipe replacement activities and leak monitoring and repair activities. Pipe Replacement By at